Process for the preparation of self-extinguishing polymers

ABSTRACT

A process for producing self-extinguishing polymers in which, during the polymerization of a styrene-based monomeric composition, there is added a bromofluorohydrocarbon (alkane) of the general formula:

United States Patent 91 Lanzo et a].

[ 1March 20, 1973 PROCESS FOR THE PREPARATION OF SELF-EXTINGUISHINGPOLYMERS [75] Inventors: Rosario Lanzo, Mantova; Nicolino Rainaldi,Mestre, both of Italy [73] Assignee: Montecatini Edison S.p.A., Milan,

Italy [22] Filed: April 8, 1970 [2,1] App]. No.: 26,794

[30] Foreign Application Priority Data April 10, 1969 ltaly ..15341 A/693,271,344 9/1966 Lowes, Jr. ..260/29.6

2,760,947 8/1956 Werkema et al. ..260/33.8 2,863,848 12/195 8 Robitscheket a] .260/ 869 2,678,953 5/1954 Conly ..260/653 3,093,599 6/1963Mueller-Tamm et al ..260/2.5 2,757,212 7/1956 Cleaver et al. ..260/653Primary ExaminerDonald E. Czaja Assistant ExaminerR. A. WhiteAttorney-Karl F. Ross 57 ABSTRACT A process for producingself-extinguishing polymers in which, during the polymerization of astyrene-based monomeric composition, there is added abromofluorohydrocarbon (alkane) of the general formula:

wherein n is a integer ranging from 1 to 8, y is greaterthanxandx+y=2n+2.

3 Claims, No Drawings PROCESS FOR THE PREPARATION OF SELF EXTINGUISHINGPOLYMERS FIELD OF THE INVENTION Our present invention relates to aprocess for producing nonflammable, noncombustible or selfextinguishingsynthetic-resin compositions, and improved self-extinguishing productsmade by this process; more particularly, the invention relates to thepreparation of self-extinguishing styrene-based polymers. a

' BACKGROUND OF THE INVENTION One of the most important physicalproperties of synthetic resins or polymers is the resistance thereof tocombustion, this property being significant in the use of the polymersin the home or in industry and wherever it is possible that productsmade from the polymers may be exposed to fire or flame.

It has been proposed to reduce the combustibility, burning rate andinflammability of polymeric compositions by incorporating thereincompounds such as organophosphates and halogen-containing substanceshaving a high heat capacity and the tendency to produce gaseoussubstances which blanket the combustion site and prevent access ofoxygen thereto.

These compounds, generally mixed with the previously polymerizedcompositions have been found to be inconvenient to use and to adverselyaffect important physical properties of products made from the polymers.

When chlorine-based compounds are supplied as the additive capable ofmaking the composition self-extinguishing for reducing the combustionrate, it has been found to be necessary to have a chlorine content of topercent by weight and it has been observed further that considerablyless bromine (e.g. 2 to 6 percent by weight) may be used whenbromine-containing compounds are provided to reduce flammability andcombustion rate. Even these quantities of self-extinguishing additiveshave been associated heretofore with diminution of the physicalproperties of the compositions.

When the term self-extinguishing is used herein, it is intended therebyto describe the property of a material which permits the latter toextinguish any combustion flame which may have been created therein.

Of course, the self-extinguishing properties of the material are relatedto the flammability thereof, the combustion rate and the rate to whichany established combustion is terminated.

OBJECTS OF THE INVENTION It is, therefore, a principal object of thepresent invention to provide a method of or process for the productionof polymeric compositions having good physical properties andhomogeneity as well as a highextinguishing rate and self-extinguishingcharacteristics, it being noted that conventional compositions andproducts containing self-extinguishing additives have heretofore beencharacterized by a reduction in quality and homogeneity.

It is another object of this invention to provide a method of or aprocess for producing styrene-based polymers of good self-extinguishingcharacteristics and low combustion rate.

Another object of the invention is to provide styrenebased polymers andproducts made therefrom with high-quality homogeneous characteristicsand selfextinguishing properties.

I SUMMARY OF THE INVENTION These objects and others which will becomeapparent hereinafter are attained, in accordance with our presentinvention, by the polymerization of a styrenebased monomeric componentin the presence of a styrene-polymerization catalyst and understyrenepolymeri'zation conditions in the presence, duringpolymerization, of a self-extinguishing additive in the form of abromofluorohydrocarbon (bromofluoroalkane) having the general formulawherein n is an integer ranging from 1 to 8 inclusively, x and y areintegers with y being greater than x and x y=2n=2. Whenn= l,x+y=4andfor2s n s 8,x y 2n 2 or 6 to 18. In any case, the ratio y/x is greater thanunity.

Best results are obtained with compounds of this general formula whereinn 2 especially CF Br CFgBI.

While applicants are not fully able to explain why these compounds havesurprisingly greater effectiveness when incorporated in the polymerduring the polymerization step than otherwise and are surprisingly moreeffective than other bromine-containing compounds no matter howincorporated, it is believed that the effect is due in part to themolecular weight of the styrenic compositions and additives and 'acontribution to improved surface characteristics and appearancecontributed in part by the self-extinguishing additives.

The additives appear somehow to become involved in the polymerizationprocess and to contribute to the polymer in more than self-extinguishingproperties and can be included in amounts of 0.1 to 10 and preferably0.5 to 4parts by weight per lOO parts by weight of the monomericcomponent without substantially diminishing the desired physicalproperties or molecular weight of the styrene-based polymers thusproduced.

The styrene-based polymers according to the present invention includepolymers consisting in whole or in part of polystyrene or styrenegraftpolymerized or copolymerized with other monomers of the vinyl type.Preferably styrene constitutes the major :proportion of the monomericcomponent i.e.'is present in an amount of at'least 50 percent by weightin the monomeric component.

Styrene, as this term is used here, includes'the unsubstituted compoundvinyl-benzene as well as substituted styrenes in which the substituent(e.g. a halogen, alkyl or another vinyl group or an aralkyl) group isplaced on the benzene nucleus or in the vinyl group.

The monomeric component may thus contain up to 50 percent vinyl orvinylidene compounds and compounds with'similar unsaturation.

The monomeric component may contain as-part or all of the styrene:alphamethylstyrene, methylstyrene, ethylstyrene,monochlorostyrene,dichlorostyrene and like alkyl styrenes, halo-styrenes,

As compounds copolymerizable with the styrene component there may belisted acrylonitrile, methacrylonitrile, the alkylesters of acrylic andinethacrylic acid such as methylmethacrylate and the respective edges of25.4 mm. One end of the specimen was clamped in accordance with thespecified standard and a Bunsen-burner flame brought toward the free endwith combustion continuing until the flame pressure-molding in arectangular mold having dimension of 200 X 200 X 6.2 mm. MOlding wasdone with heating of the mold for a period of 10 minutes at 135 Crectangular configuration were milled to a size of 12.7 X 6.35 X 127mms. The test was performed in accordance with ASTM Standard D 635-56-Twith the specimen was held at an inclination of 45 to the horizontal inaccordance with this standard. Two notches were marked on the specimenwith spacing from one another of 76 mm and a distance from the From theplates thus obtained, test specimens of 55 like- 5 reached the firstnotch. The Bunsen burner was then The self-extinguishing additives alsomay be incorremoved and the specimen allowed to burn without inporatedin styrene-based compounds (polymers and/or duced combustion until theflame was extinguished. copolymers) of the types produced bypolymerizing The burned portion was measured starting from the styreneand/or its substituted derivatives along or in adsecond notch calibratedsuch that a distance of 0 mixture with unsaturated compounds of thevinyl corresponding to no combustion. The time required for and/orvinylidene type, with synthetic or natural the combustion distance wasalso determined. rubber. This group of compounds, which may be made TheTable contains the results of the test together self-extinguishingaccording to the invention, includes with the molecular weight asdetermined by the Standhigh-impact polystyrene andstyrene-butadieneinger method of the precipitated polymer, the residualacrylonitrile (ABS) terpolymers. High-impact commonomer and thesolubility of the polymer in methanol positions according to thisinvention may also be made are given in the accompanying table. Themolecular by mixing or blending styrene-based polymers containweight wasdetermined from measurements of specified ing the additive withhigh-impact polymers which have viscosity at 25 C of a solution of thepolymer in been polymerized without the presence of the toluene (2 gramsper liter) in accordance with the relabromofluoroalkanes specifiedearlier. tionship E1 2.89 X 10 p. where H is the calculated averagemolecular weight and p. is the specific viscosi- EXAMPLE 'ty. Residualmonomer (styrene) was determined by A master batch is prepared byblending 100 parts by Spectrophotometric analysis weight of monomericstyrene with 0.09 parts by weight Tests A through C are given comparisonWhile of tertiary-binyLperbenzoate (catalyst system); the tCSt D throughG illustrate the use Of?! self-extinguishlfl xtinguishing compound i f htype d i h ing agent according to the present invention. Test Aquantities given in Table l infra. was carried out with noself-extinguishing agent while Polymerization was carried out in glassflasks which test B and C Show he esults Obtained when convenwere flu hd ith it id d ith th master tional self-extinguishing agents were usedas indicated. batch and the self-extinguishing compounds, hermeti- ACOmPRIiSOnOf tests B and C with tests D to G demoncally sealed andplaced in a thermostatically controlled straw that e f-extinguishingproperties are obtainable bath, Th t rat f th b th wa mai t i d f 9without substantial molecular weight reduction and it is hours at C,fori4 hours at C, for 3 hours at noted that the characteristics of thepolymer with the forl hour at C, for 1 hour at C, for 2 hours at systemof tests D through G are vastly superior to the C. 35 polymer resultingfrom tests B and C.

Test A B c 1) E F G Self-extinguishing additive:

Tris-24$ dibromo-propyl-phosphate, percent by weight. of styrene 2 4CFzBr-ChBr, percent by weight 01 styrene 1 1. 5 z 4 Chemical-physicalcharacteristics:

Molecula weight 71,900 57, 700 59,300 66,100 66,000 59,500 57,500Residual monomeric styrene, percent 2. 5 3 1.1 1. 4 2 2. 5 l. 5Percentage solubility in methanol... 3. 0 4. 8 5, 2 3, 2 4 5 5 3 6Self-extinguishing characteristics:

Length of burned specimen in mm 76 76 0 76 34 1 0 Combustion rate inmmJsec 23 19 0 17 17 16 0 Evaluation Burns Burns Burns 1) 1 Does notburn. I Self-extinguishing.

At the conclusion of this period, the flasks were emp- We claim: tiedand the polymeric mass thoroughly ground. Plates l. A self-extinguishingpolystyrene composition were prepared from the powder of each sample by50 produced by polymerizing styrene in the presence of an effectiveamount of symmetrical dibromotetrafluoroethane.

2. The composition defined in claim 1 wherein said symmetricaldibromotetrafluoroethane is used in an amount of 0.1 to 10 parts byweight per 100 parts by weight of the styrene.

3. The composition defined in claim 2 wherein said symmetricaldibromotetrafluoroethane is used in an amount of 0.5 to 4 parts byweight per 100 parts by weight of the styrene.

2. The composition defined in claim 1 wherein said symmetricaldibromotetrafluoroethane is used in An amount of 0.1 to 10 parts byweight per 100 parts by weight of the styrene.
 3. The compositiondefined in claim 2 wherein said symmetrical dibromotetrafluoroethane isused in an amount of 0.5 to 4 parts by weight per 100 parts by weight ofthe styrene.